The term “antifuse” is used to indicate an electrical circuit having behaviour opposite or complementary to that of a fuse.
A fuse is a component that presents a low resistance (e.g., it basically behaves like a short circuit) and, for example when the current that passes through it reaches a certain triggering threshold, “opens” or “burns”, thus presenting a high resistance (e.g., it basically behaves like an open circuit, interrupting passage of current).
Instead, an antifuse presents a high resistance (e.g., it basically behaves like an open circuit) and, following upon an activation event, for example, when the voltage across it reaches a certain breakdown threshold, in the antifuse a (low-resistance) conductive path is created, so that the antifuse behaves like a conductive line.
Underlying the activation event there may be a phenomenon of dielectric breakdown. Such a phenomenon is brought about when a dielectric material subjected to a sufficiently high electrical field ceases to be insulating. In the solids, dielectric breakdown can be put down to an electrostatic discharge due to exceeding of the dielectric strength.
The antifuse may comprise a thin barrier of a dielectric material set between two metal conductors (in practice a capacitor). When a sufficiently high voltage is applied between these conductors, the dielectric layer may convert into a low-resistance, and hence conductive, material.
A possible field of application of antifuses is represented by (permanent) programming of semiconductor circuits, for example, integrated circuits such as memories. For instance, some programmable logic circuits such as ASICs may use antifuse technology for configuring logic circuits. A possible sector of application of antifuses is represented by non-volatile memories (NVMs), for example, in devices of the type referred to as Systems-on-Chip (SoCs).
Notwithstanding the extensive activity of innovation and research in the sector, there is still felt the need to provide antifuse solutions improved in terms of area of silicon occupied, reliability, and range of operating temperatures. For example, in sectors of application such as the vehicle sector, a factor to be taken into account in cell-antifuse implementations may be represented by the fact that, during programming, the cells that are not to be programmed may in any case be subjected to an electrical field of a certain importance (for example, equal to half the nominal electrical field), thus undergoing stresses.
This may constitute a risk from the standpoint of reliability. The inhibition times may prove longer than the individual programming so that there may arise the risk of undesired programmings in defective antifuse cells.